When using a thermocouple as a temperature sensor, the output voltage of the thermocouple provides an indication of the difference in temperature between the hot and cold junctions of the thermocouple. Accordingly, in order to accurately determine the absolute temperature of the hot junction, it is necessary to know the temperature of the cold junction. In many applications, the cold junction is at room or ambient temperature and therefore varies considerably. As a result of such variation, it becomes highly desirable to provide a means for measuring the instantaneous ambient or room temperature.
As a result of recent advances in micro-computer technology, it has become feasible to utilize micro-computers as control systems for household and other appliances. When utilizing such systems, it is necessary to interface analog temperature sensors (such as thermocouple) to the digital inputs of the micro-computer. To this end, the art has developed several analog to digital converter circuits for such interfacing. One example of such circuitry is U.S. Pat. No. 3,826,983.